chapter 7 bone tissue anatomy

What is osteology?

The study of bone.

List the six functions of the skeletal system.

1. Support 2. Protection 3. Movement 4. Electrolyte balance 5. Acid-base balance 6. Blood formation

What is bone tissue also known as?

Osseous tissue.

What process hardens the matrix of bone tissue?

Mineralization or calcification.

What are flat bones and give examples?

Flat bones enclose and protect soft organs and provide broad surfaces for muscle attachment. Examples include cranial bones, ribs, sternum, scapula, and hip bones.

What are long bones and provide examples?

Long bones are crucial for body movement. Examples include the humerus, radius, ulna, femur, tibia, fibula, metacarpals, metatarsals, and phalanges.

What defines short bones and give examples?

Short bones are nearly equal in length and width. Examples include carpal (wrist) and tarsal (ankle) bones.

What are irregular bones and provide examples?

Irregular bones have shapes that do not fit into other categories. Examples include vertebrae and middle-ear bones.

What is the structure of a long bone?

A long bone consists of an outer shell of compact bone, a medullary cavity, and spongy bone at the ends.

What is the diaphysis of a long bone?

The shaft of the bone that provides leverage.

What is the epiphysis of a long bone?

The expanded head at each end of the bone that strengthens the joint and provides surface area for tendon and ligament attachment.

What covers the joint surface of bones?

Articular cartilage, which enables smooth joint movement.

What is the periosteum?

A sheath covering the bone, consisting of an outer fibrous layer and an inner osteogenic layer.

What is the endosteum?

A thin layer of reticular connective tissue lining the internal marrow cavity and covering spongy bone.

What are osteogenic cells?

Stem cells that give rise to most other bone cells, found in the endosteum and periosteum.

What do osteoblasts do?

Bone-forming cells that synthesize the organic matter of the bone matrix.

What are osteocytes?

Former osteoblasts trapped in the bone matrix, residing in lacunae and connected by canaliculi.

What is the function of osteoclasts?

Bone-dissolving cells that resorb bone matrix.

What is the significance of the epiphyseal plate?

A zone of hyaline cartilage that allows for the lengthening of bones in children and adolescents.

What is diploe?

The spongy layer of a flat bone, which absorbs impact and protects the inner layer.

What is the role of osteocalcin?

A hormone secreted by osteoblasts that stimulates insulin secretion and regulates fat storage.

What is the composition of bone tissue?

Bone tissue consists of cells, fibers, and ground substance.

How do osteocytes contribute to bone homeostasis?

They resorb and deposit bone matrix, helping to maintain bone density and blood calcium levels.

What is the primary function of compact bone?

To provide strength and support to the skeleton.

What is the medullary cavity?

The central space within a long bone that contains bone marrow.

What are nutrient foramina?

Minute holes through which blood vessels penetrate into the bone.

What is the relationship between osteoblasts and osteogenic cells?

Osteoblasts arise from the differentiation of osteogenic cells.

What is the composition of the matrix of osseous tissue?

About one-third organic (collagen and protein-carbohydrate complexes) and two-thirds inorganic matter (85% hydroxyapatite, 10% calcium carbonate, and other minerals).

What is hydroxyapatite?

A crystallized calcium phosphate salt that makes up a significant portion of the inorganic matter in bone.

What happens to bones that are deficient in calcium salts?

They become soft and bend easily, leading to conditions like rickets.

What is the role of collagen in bone?

Collagen provides flexibility to bone; without it, bones become excessively brittle, as seen in osteogenesis imperfecta.

What is an osteon?

A structural unit of compact bone, consisting of concentric lamellae arranged around a central (haversian) canal.

How are collagen fibers arranged in the matrix of a lamella?

In a helical pattern, with alternating directions in adjacent lamellae to enhance bone strength.

What is the function of canaliculi in bone?

They connect osteocytes to each other and to the central canal, facilitating nutrient and waste exchange.

What is spongy bone, and how does it differ from compact bone?

Spongy bone consists of a lattice of slivers called spicules and thin plates called trabeculae, providing strength with minimal weight.

What are the two types of bone marrow?

Red marrow (produces blood cells) and yellow marrow (fatty tissue that can revert to red marrow in certain conditions).

What is ossification?

The process of bone formation, which occurs through intramembranous and endochondral ossification.

What bones are formed through intramembranous ossification?

The flat bones of the skull and the clavicle.

What are the stages of intramembranous ossification?

1. Mesenchyme condenses into soft tissue. 2. Osteoblasts secrete osteoid tissue. 3. Calcium phosphate crystallizes. 4. Periosteum forms and compact bone develops.

What is endochondral ossification?

A process where bone develops from a preexisting model of hyaline cartilage, forming most bones in the body.

What occurs during the primary ossification center in endochondral ossification?

Chondrocytes inflate and die, and osteoblasts form a bone collar around the cartilage model.

What is the metaphysis?

The region of transition at each end of the primary marrow cavity during bone development.

What happens to the epiphyses during infancy and childhood?

They fill with spongy bone, and cartilage is limited to the articular surfaces and the epiphyseal plate.

What is the significance of the helical arrangement of collagen fibers in bone?

It enhances the strength of the bone, similar to the construction of plywood.

How does blood flow through the skeleton?

About half a liter of blood per minute passes through, with vessels entering through nutrient foramina and connecting to central canals.

What are interstitial lamellae?

Irregular regions of old osteons that have broken down as the bone grows and remodels.

What is the role of osteoclasts in bone development?

They digest calcified tissue, creating the primary marrow cavity and facilitating bone remodeling.

What is the function of trabeculae in spongy bone?

They are arranged along lines of stress to impart strength while minimizing weight.

Where is red marrow found in adults?

In the skull, vertebrae, ribs, sternum, part of the pelvic girdle, and proximal heads of the humerus and femur.

What happens to yellow marrow in cases of severe anemia?

It can transform back into red marrow to assist in blood cell production.

What type of cartilage is limited to the articular surfaces and epiphyseal plates?

Articular cartilage

What is the primary function of the epiphyseal plate?

Bone elongation during childhood and adolescence

What happens to the epiphyseal plate by the late teens to early twenties?

It closes, uniting the primary and secondary marrow cavities into a single cavity.

What is the process by which cartilage converts to bone?

A five-stage process involving zones of reserve cartilage, cell proliferation, cell hypertrophy, calcification, and bone deposition.

What is the zone of reserve cartilage?

The area where hyaline cartilage has not yet transformed into bone.

What occurs in the zone of cell proliferation?

Chondrocytes multiply and arrange into longitudinal columns of flattened lacunae.

What happens in the zone of cell hypertrophy?

Chondrocytes cease dividing and enlarge.

What is the significance of the zone of calcification?

Minerals are deposited in the matrix, calcifying the cartilage.

What occurs in the zone of bone deposition?

Walls between lacunae break down, chondrocytes die, and osteoblasts deposit new bone.

What is interstitial growth?

The growth of cartilage from within the metaphyses.

What is the epiphyseal line?

A line of spongy bone marking the site of the original epiphyseal plate.

What is appositional growth?

The process by which bones grow in diameter and thickness.

How do osteoblasts contribute to appositional growth?

They deposit osteoid tissue that calcifies and traps them as osteocytes.

What is Wolff's law of bone?

The architecture of a bone is determined by the mechanical stresses placed upon it.

What is mineral deposition?

A process where calcium, phosphate, and other ions are taken from blood plasma and deposited in bone tissue.

What role do osteoblasts play in mineral deposition?

They lay down collagen fibers that become encrusted with minerals.

What is ectopic ossification?

Abnormal calcification that occurs in other organs, such as arteriosclerosis.

What is mineral resorption?

The process of dissolving bone to release minerals into the blood.

How do osteoclasts carry out mineral resorption?

By secreting hydrogen ions and acid phosphatase to dissolve bone minerals and digest collagen.

What is the normal range for calcium concentration in blood plasma?

9.2 to 10.4 mg/dL

What is hypocalcemia?

A calcium deficiency that can cause excessive excitability of the nervous system.

What symptoms can arise from severe hypocalcemia?

Muscle tremors, spasms, or tetany, and potentially laryngospasm.

What is hypercalcemia?

A calcium excess that can cause nerve and muscle cells to become less excitable.

What is the role of the skeleton in calcium homeostasis?

It acts as a reservoir for calcium and phosphate.

What is the stable pool of calcium in bones?

Calcium incorporated into hydroxyapatite that is not readily exchangeable.

What is the exchangeable calcium reserve?

Calcium that is easily released into the tissue fluid.

What blood calcium concentration level indicates hypercalcemia?

12 mg/dL and higher

What are some symptoms of hypercalcemia?

Emotional disturbances, muscle weakness, sluggish reflexes, and sometimes cardiac arrest.

What can cause hypocalcemia?

Vitamin D deficiency, diarrhea, thyroid tumors, or underactive parathyroid glands.

Who is at risk for hypocalcemia due to calcium demands?

Pregnant and lactating women.

What is the leading cause of hypocalcemic tetany?

Accidental removal of the parathyroid glands during thyroid surgery.

What three hormones regulate calcium homeostasis?

Calcitriol, calcitonin, and parathyroid hormone.

How is calcitriol produced?

Through the sequential action of the skin, liver, and kidneys.

What is the primary function of calcitriol?

To raise blood calcium concentration.

How does calcitriol increase blood calcium levels?

By increasing calcium absorption in the small intestine, promoting osteoclast activity, and enhancing calcium reabsorption in the kidneys.

What role does calcitonin play in calcium regulation?

It lowers blood calcium levels by reducing osteoclast activity and increasing osteoblast activity.

What triggers the secretion of parathyroid hormone (PTH)?

A drop of 1% in blood calcium levels.

What are the four mechanisms by which PTH raises blood calcium levels?

Increases osteoclast population, promotes kidney calcium reabsorption, stimulates calcitriol synthesis, and inhibits collagen synthesis by osteoblasts.

What is the normal phosphate concentration range in plasma?

3.5 to 4.0 mg/dL.

How does calcitriol affect phosphate levels?

It raises phosphate levels by promoting its absorption from the small intestine.

What is a stress fracture?

A break caused by abnormal trauma to a bone, such as from falls or athletics.

What is a pathologic fracture?

A break in a bone weakened by disease, such as bone cancer or osteoporosis.

What are the four stages of fracture healing?

Formation of a hematoma, formation of a soft callus, conversion to a hard callus, and remodeling.

What occurs during the formation of a hematoma?

Blood forms a clot at the fracture site, which is invaded by fibroblasts, macrophages, and osteogenic cells.

What is the role of osteoblasts during fracture healing?

They produce a bony collar called the hard callus around the fracture.

What is the purpose of immobilizing a broken bone during healing?

To prevent reinjury.

What is osteoporosis?

A bone disorder characterized by decreased bone density and increased fracture risk.

What is the effect of anabolic steroids on bone growth in adolescents?

They can cause premature closure of epiphyseal plates, resulting in short adult stature.

What is the typical healing time for uncomplicated fractures?

8 to 12 weeks.

What is the role of traction in fracture treatment?

To treat fractures of the femur in children by overriding the force of thigh muscles.